Best tactic is to let you offense occupy the empy field spaces of you opponents defense and match your defense with your opponents offense.
So in a 4-1-2-1-2 diamond, occupy the red stripes:
----ST-----ST----
-------AMC-------
----MC-----MC----
-------DMC-------
DL--DC-----DC--DR
Your formation should look some thing like:
--------ST--------
---AMC----AMC---
--------MC--------
DML----DMC----DMR
----DC--DC--DC---
Red-arrowing your DML and DMR
Or
--------ST--------
---AMC----AMC---
ML-----MC-----MR
-------DMC-------
----DC--DC--DC---